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"Poisonous" does not mean deadly. Some manifestations of toxicity are subtle. The dose, as always, determines if a plant is safe source of nutrients or a toxic hazard.

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BRIEF: Are Oleander plants harmful to horses?

How can I determine if Oleander plants will be harmful to horses if planted near their pastures.


Nerium oleander is quite toxic to all mammals that have been known to ingest it. This is the most common type of oleander and has pink, white or red blossoms. Another species, , is called yellow oleander and it is also toxic, but not at the same dosage. Horses should not have access to either plant. If the plants are on a neighbor's property and out of the reach of the horses in the pasture, then all you have to do is keep your horses out of the neighbor's yard. If they are on your own place, and your horse may walk by or be tied near them, then I would get rid of them. They don't look appetizing to most horses, but a few mouthfulls of Nerium oleander is all it would take to kill.